In known grinding machines, the part to be machined is secured in a part carrying spindle in order to be driven in rotation around its axis of revolution, the spindle forming part of a headstock which is fixed to the framework of the machine. On the framework is further arranged a movable slide runner including a grindstone. The slide runner can be displaced generally by means of a digital control arrangement along a longitudinal and a transversal axis respectively oriented parallel and perpendicularly to the axis of revolution of the part to be machined which is also the rotation axis of the spindle. The displacement of the slide runner along the transversal axis enables bringing the grindstone, the axis of rotation of which is normally parallel to that of the spindle, into contact with the part to be machined in order to reduce its diameter to a desired value over a length corresponding to the longitudinal displacement of such slide runner. As is well understood, the two displacements of the slide runner can be programmed in a manner such that the piece exhibits a profile of predetermined form.
Such machines enable machining under good conditions of parts for which the ratio length-over-diameter, which ratio will be hereinafter designated by K, does not exceed approximately 10.
The grinding of parts exhibiting a ratio K greater than 10 is possible, but by means of so-called centerless machines. FIG. 1 shows the principal elements of such a machine seen in profile. The part to be machined 1 rests on a support 2 whilst being gripped by a roller 3 and a grindstone 4. As is well understood, the part includes a center, but the position of the center is not fixed since it depends on the diameter of the part, this particularity thus justifying the name given to such type of machine. The roller 3, the surface of which exhibits a high coefficient of friction, turns in the sense inverse to that of the grindstone 4, such sense being chosen in a manner such that the roller and the grindstone urge the part 1 onto support 2. In such conditions, the roller drives the part 1 in rotation and renders possible its machining by the grindstone. Such machines enable machining cylindrical parts of about 1 millimeter diameter minimum over a length of several centimeters, which length is equal to the width of the grindstone. The corresponding ratio K can thus attain 100 at best.
The present invention proposes to provide a grinding machine having machining possibilities clearly more extensive, in particular as far as concerns the ratio K, than the combined possibilities of existing machines.